I haven't taken a Manhattan course, but bought the SC guide to help with my preparation. I am extremely impressed with the quality of the Manhattan GMAT tests and how closely they represent the actual GMAT. The CAT algorithm is a cut above that of all the other testing companies and is second only to GMATPrep. The difficulty of the quantitative sections helped me to focus on my weaknesses and definitely played a part in improving my quantitative score. I am glad I purchased the Manhattan Guide and did the Manhattan tests.

Here is a breakdown of my scores on the practice tests:
MGMAT CAT 1 - 680 (Q48, V35)
MGMAT CAT 2 - 680 (Q48, V35)
MGMAT CAT 3 - 680 (Q43 - did not finish, left three questions unanswered, V39)
MGMAT CAT 4 - 720 (Q47, V42)
MGMAT CAT 5 - 790 (Q50, V51)
MGMAT CAT 6 - 800 (Q51, V51)

GMATPrep Test 1 - 750 (Q50, V - can't remember, don't know how to see the score again, but I got 8 questions wrong)
GMATPrep Test 2 - 770 (Q50, V47)

Congrats on the fine score Chris:)

what was your math prep like and how were the questions in the quants section & in the test overall ?

I have pretty decent foundations in Math, so the Quant section wasn't much of a problem on the GMAT. I used the 4GMAT guides to view probability, number theory, and geometry. Once I started doing the Manhattan tests, I found some deficiencies in modulus operations and reviewed those from the internet.
As far as the test, I panicked a little at around question 11 as I wasn't seeing hard questions. I was pretty sure I got everything correct up to then, but was worried that the difficulty really wasn't increasing. By question 17, I started getting tougher questions and relaxed a little. I just remember reading on a large number of posts on various forums that you should start seeing tough questions by question number 7/8, but I guess this observation might be relative.
Overall, the test experience was relaxing once I got the nerves out. The scratch pad was easy to use (I was a little worried about this aspect). The staff at the center were friendly and professional.

Thankyou Chris for the immediate response.

I have also bought the 4gmat math guides - but i found them way too exhaustive and haven't used them much ( i felt they had content that was beyond the scope of Gmat ) now that my exam is nearing i feel jerky in quants( inspite of a decent math background )

Do you think it would be a good thing to use the math part of the 4G guides to bolster the math preparedness ? also, at what gaps did you take each of the practise tests ?

Thanks again !

Congrats Chris! You score is decent in verbal too. And I saw you improved a lot in the later CATs of MGMAT. Do you have strong background in verbal too. Any tips?

Sankar, you are correct in that the 4GMAT guides are pretty exhaustive. I should have qualified their use. I did not use them for practice, but used them for the little time saving tricks they provide. For instance, they have a neat little formula for the number of factors of an integer and multiplicity of integers. I memorized some of these tricks and they did save time on both the real exam and the practice tests.
As far as tests, I did two MGMAT or 1 MGMAT and 1 GMATPrep a week. I made sure I thoroughly reviewed all my mistakes. I kept a log of all the mistakes I made and printouts of all the problems (quant and verbal) that I got wrong. I redid these problems over and over again until the concepts sunk in. Although, the MGMAT and GMATPrep were my primary resource for testing material, I did do some 800Score tests (scored between 600-680) and Kaplan tests (630-700). I didn't pay much attention to the latter as I found them to be either too hard (in terms of time) or just not representative of the real test.

As far as verbal, I was disappointed with my score, I wanted to score higher as I thought I improved to a greater extent. My accuracy in CR and RC was pretty good so I didn't change anything there. After MGMAT CAT 2, I switched my SC strategy from 2/3 splits and finding what sounds best to actually trying to find the mistake in the original. There are only a few mistakes that the GMAT disguises and repeats over and over again. Once I found this mistakes in the original sentence, I wrote them down and looked for the answer choices that best correct them. For this idea, I must thank Manhattan. They first explain what is wrong in the original sentence in all of their SC solutions. After employing this strategy, I found a marked increase in my SC accuracy.